1. Field of the Invention
The present invention relates to a circuit board connector for interfacing between a passive backplane or motherboard and a circuit board mated to the backplane or motherboard. More specifically, the present invention is a circuit board connector which reduces the ground potential difference between a circuit board, such as a single board computer (hereinafter "SBC"), and a passive backplane, by defining a number of pins which are grounded and a number of pins which are connected to VCC. The circuit board connector also includes bus select pins which permit the circuit board to select a particular bus, such as a PCI bus, connected to the backplane.
2. Description of the Related Art
Conventionally, SBCs are connected to passive backplanes via industry standard architecture (hereinafter "ISA") connectors. Problems arise with such an arrangement, however, due to a ground potential difference which exists between the ground on the SBC and the ground on the passive backplane.
More specifically, the ground potential difference noted above adversely affects data transmissions between the SBC and the passive backplane. For example, the ground potential difference can cause noise, bit drop-out (i.e., loss of bits), and spurious bits to appear in a data transmission. These problems become worse as the number of connectors on the passive backplane and the processing speed of the SBC increase, and even become more acute when the number of connectors is greater than 10 and/or the processing speed of the SBC is greater than 100 MHz.
Problems similar to those described above occur in slimline or low profile chassis computers, in which circuit boards are connected to a motherboard via a riser card. In such cases, as in the case of the passive backplane described above, a ground potential difference exists between the circuit boards and the motherboard, which can adversely affect data transmitted therebetween.
In some high data throughput applications, data corruption resulting from a ground potential difference can be tolerated. However, such data corruption is not desired in cases where data integrity is essential, such as in processing auditory signals through, e.g., text-to-speech applications or interactive voice response cards. For example, in the case of text-to-speech processing, bit drop-out, spurious bits, and noise can cause speech generated from processed data to be unrecognizable.
Heretofore, there has been no way of alleviating the foregoing problem in a cost-effective manner, since the ground potential difference described above was a direct result of the limited number of pins on an ISA connector. That is, standard ISA connectors include only three VCC pins, four ground pins, and a limited number of unassigned pins. Even if all the unassigned pins in a standard ISA connector were re-assigned to VCC and ground, it has been determined that it would still be insufficient to reduce the ground potential difference noted above enough to alleviate data drop-out, spurious bits, and noise, especially in cases where the SBC has a processing speed in excess of 100 MHz and/or the number of connectors on the passive backplane exceeds 10.
In addition to the foregoing problems related to the ground potential difference, conventional ISA connector/passive backplane arrangements also make it difficult for an SBC to select a bus on the backplane, over which to transmit data. That is, since a standard bus connector includes only two non-assigned pins, in cases where more than two buses are connected to a backplane (e.g., four buses), it was necessary to add physical components, such as jumpers, between bus connectors so as to allow the SBC to select a particular bus. These physical components reduced the amount of space available on the backplane and increased production costs.
Thus, there exists a need for a circuit board connector which provides (1) additional VCC and ground pins so as to reduce a ground potential difference between a backplane (or motherboard as the case may be) and a circuit board installed on the backplane, and (2) bus select pins for selecting a bus connector/bus, without the need for additional physical components, such as jumpers.